One type of viral vaccine contains inactivated viruses. Active or infectious viruses can be inactivated so they no longer are infectious and can no longer replicate to produce progeny viruses. To be effective in a vaccine, however, inactivated viruses still must retain their ability to stimulate an immune reponse (i.e., retain immunogenicity) when administered to a subject.
Different methods exist for inactivating rotaviruses. In one method, rotavirus may be inactivated using chemicals. In one example, beta-propiolactone may be used as the chemical.
In another method for inactivating rotaviruses, heating the rotavirus (thermal inactivation) may be used. In known methods for heat inactivating rotaviruses, the viruses are isolated or purified from the environment in which they are typically found prior to thermal inactivation. In one example, rotavirus propagated on cultured cells is isolated from the cell culture medium or supernatant in which the virus unfected cells had been grown, prior to heat or thermal inactivation (PCT Publication No. WO2009/032913). In one example, the isolated rotaviruses are then suspended in an aqueous buffer having a specific osmolality (e.g., 200-500 mOsm), a specific concentration of a salt of a divalent cation (in the range of about 1 mM to 15 mM), and a specific amount of sugar and/or sugar alcohol (in the range of about 1 to 20% w/v) (PCT Publication No. WO2009/032913). The isolated rotaviruses, suspended in the aqueous buffer having the specific osmolality, divalent cation concentration and sugar/sugar alcohol concentration, is then thermally inactivated.